I got it as a resto in tanking proving grounds, wasn't too difficult after knowing each wave
But it was something like year ago, I don't play my shaman as a main anymore, so I'm afraid I won't be able to tell you more details

I did the tank one as resto like 8 months ago, here's the video: https://www.youtube.com/watch?v=x4AL92FUhJw
This was the only time I felt conductivity was useful this expansion, since having a lot of throughput and having a lot of mana is your top priority.
Also make sure you use the totemic recall glyph, it's really useful.
I used a high crit build with 2x regen trinkets (darkmoon healer one and the blackfuse one).
It's all about using your cc abilities properly and timing your heals correctly.

Basically, Capacitor Totem is your best friend, and along with Call of Elements I used it on heavy AoE packs (mostly those virmen) and when mantids aggro'ed me. Hex whenever the NPC doesn't do damage to the target. With Primal Elementalist use Fire Elemental for the first mantid wave, use earth elemental for the last wave. Summoning Earth Elemental basically wins the wave. Other than that is just proper cooldown usage, interrupts and grounding totems.